The delights of flower painting: making colours that survive the centuries

From Richard Mulholland

With the Chelsea flower show in full swing, it’s a good time to return to the subject of the great 18th century botanical painter, Ferdinand Bauer, his paintings for one of the most splendid illustrated Floras ever produced, and the mysterious colour code he used to produce his paintings. Bauer, along with his equally talented brother Franz, is considered to be amongst the greatest botanical painters, and his work for the Flora Graeca (published 1806-1840) amongst the most impressive achievements in natural history painting.

Bauer, as we discovered in the last post , was John Sibthorp’s chosen travelling artist on his expedition to Greece and the Levant in 1786. Sibthorp’s desire was to document the flora of the Eastern Mediterranean, following in the footsteps of Joseph Pitton de Tournefort, and updating Dioscorides’ De Materia Medica, the 1st century medical treatise that had been a standard text on the subject for over 1600 years.

When he came to Oxford in 1787, Bauer spent six years painting almost 1500 life-size watercolour paintings of plants and animals with astonishing colour accuracy – over 960 of these for the Flora Graeca. He did not paint in colour in the field, and reproduced his sketches in colour in his studio in Oxford using for reference only his memory, the dried specimens he and Sibthorp had collected, and a series of brief pencil sketches annotated with numerical colour codes that may have referred to a painted colour chart.

The Sherardian Library of Plant Taxonomy at the Bodleian has all of Bauer’s original watercolour paintings, most of his field sketches and most of the original herbaria specimens from the expedition. However, although there is evidence of a very early colour chart that may have been used by Bauer, if a colour chart ever existed for the Sibthorp paintings, it has been lost. The Bodleian’s Heritage Science department are working on a significant research project, funded by the Leverhulme Trust that aims to unravel Bauer’s code by looking closely at the materials and methods he used and try to understand how he was able to achieve such veracity of colour in his work.

Painting in watercolour in the 18th century was not as it is today. Although by the 1780s, a painter might purchase boxes of ready-made watercolour cakes (George Reeves introduced portable ‘moist’ watercolour cakes in 1766 that were a vast improvement on ‘dry’ cakes used previously), most painters still bought dry colour pigments in powder form from artists’ colourmen, druggists and apothecary shops, grinding them with plant gums and water to create their paints. The end product was usually dried and stored in mussel or oyster shells, and could be reactivated with water as needed over the following few days.

The Museum of London has a Reeves watercolour box that was in the possession of British naval officer Isaac Smith, who accompanied Captain Cook on both of his expeditions. Although the box was not taken on Cook’s first voyage on The Endeavour, Smith appears to have used it on board The Resolution during the second voyage (1772-75), where the creation of surveys and maps were amongst his duties. There little evidence that professional travelling artists in the 18th century used commercial ready-made moist watercolours on their voyages, although they were popular amongst amateurs and professionals alike in the nineteenth century. The likely explanation may be that artists working in the 1770s and 80s would have learnt the art of preparing their own colours during a traditional apprenticeship and preferred to maintain their own quality control. However, the colours in this early box by Reeves are useful, as they are clearly labelled and therefore give us an insight into the watercolour pigments that were popular at the end of the 18th century, and a clue toward what we might expect Bauer to have used in his work.

The late eighteenth century also brought increased status to watercolour painting. Previously water based paints were generally used for either ‘washing’ (the hand colouring of prints and maps) or ‘limning’(the painting of portrait miniatures) or to ‘stain’ drawings. At the Royal Academy for example, watercolour was not considered in the same category as painting, watercolourists were regarded as ‘draughtsmen’, could only show their work in the lower ‘drawings’ chambers and were ineligible for full membership. In fact the Royal Academy did not admit watercolour painters as full exhibiting members until 1810.

Watercolour painting, as we think of it today however, had already emerged as a medium in its own right by the 1760s, and its status as an art form was cemented by the formation of the Society of Painters in Watercolour (now the Royal Watercolour Society) in 1804. With its newfound popularity, (especially amongst amateur painters from the nobility) from the mid-eighteenth century, numerous instructional manuals on watercolour painting were published, often concentrating on landscapes and flowers, and often containing lists of pigments recommended by the author for specific tasks.

‘The Delights of Flower Painting’ by John June, published in 1756 for example, contains a list of pigments, and instructions on how they should be prepared and used for painting flowers. With a few exceptions, most of these pigments are also contained in Isaac Smith’s watercolour box.

Such a selection of pigments would have been very familiar to Bauer, painting thirty years later, as there were few new pigments introduced to artists between the 1750s and the beginning of the 19th century. Using a number of analytical techniques, we are able to positively identify many pigments that Bauer used in his Flora Graeca paintings, and match them with his colour codes in order to ascertain whether certain numbers referred to specific pigments. The results show that Bauer’s code is certainly systematic, but also that he used a fairly traditional palette, considerably more like that of a 17th century miniaturist painter perhaps than a late 18th century watercolourist. Perhaps more surprisingly, he appears to have represented the myriad of colour seen across the Levant using only a small number of pigments in his palette.

We can pinpoint pigments by using very sensitive techniques such as Raman spectroscopy and XRF (X-ray Fluorescence spectroscopy), but using another technique – hyperspectral imaging – we are also able to ‘map’ Bauer’s pigments across an entire painting. The following example is from Bauer’s little-known Fauna Graeca paintings, equally impressive as his paintings of flowers. The false colour hyperspectral image composite highlights certain areas of the painting where he has used blue pigments. In this case, the areas that show as red indicate areas where indigo was used and areas that show as purple indicate those where a copper-based blue such as azurite was used..

Identifying the ‘what’ of course is very useful, but it doesn’t tell us everything about how Bauer worked, and in particular why he chose to use certain pigments and not others. One way to address this question is through historical reproduction – the recreation of facsimile paintings using materials and methods close to those Bauer would have used. Although Bauer is unlikely to have made his own pigments, the dry pigments we can purchase today are ground and prepared using modern techniques and are often prepared differently from those that were available in the 18th century.

Grinding vermillion pigment with a glass muller

We can get around this in many cases by manufacturing our own pigments using 18th century recipes. We know through our analysis that Bauer made extensive use of a copper-based green in his paintings of plants. In the case below, we created a batch of the copper green pigment Verdigris by exposing copper sheeting to wine vinegar over a period of time. The acetic acid in the vinegar reacts with the copper and forms an encrustation of green on the surface. This is scraped off regularly and then carefully ground into paint using a glass muller.

Making Verdigris pigment at the Bodleian

We know almost nothing about Ferdinand Bauer. There is no known portrait of him, very few letters, and almost no descriptions relating to his working procedures. However, this approach to art historical research provides an opportunity to gain an insight into his working life and perhaps a glimpse of his particular genius in creating these astonishing works of art.